Field of the Invention
This disclosure relates to an image forming apparatus that forms an image on a sheet.
Description of the Related Art
Hitherto, there have been image forming apparatuses, such as a printer, a copier, and a facsimile, which include not only a mode for forming an image on a front surface of a sheet but also a two-side printing mode for also forming an image on a rear surface of a sheet having an image formed on the front surface thereof.
In such an image forming apparatus, when the two-side printing mode is selected, a sheet having an image formed on the front surface thereof is reversed and is conveyed to a duplex conveyance path, and the sheet is conveyed again to an image forming portion so that an image is formed on the rear surface thereof.
Hitherto, JP-A-2009-75478 has proposed an image forming apparatus in which a two-side conveyance unit is provided in an apparatus body so as to be able to be opened and closed, one side of a guide member constituting a duplex conveyance path is formed in the apparatus body, the other side thereof is formed in the two-side conveyance unit, and a sheet jamming in the duplex conveyance path is able to be extracted by opening the two-side conveyance unit.
The image forming apparatus is configured such that a drive roller in a conveyance roller pair conveying a sheet on the duplex conveyance path is disposed at a fixing unit on the apparatus body side, and a driven roller is disposed in the two-side conveyance unit, thereby dividing the conveyance roller pair by the opening of the two-side conveyance unit.
In addition, the image forming apparatus is configured such that a positioning protruding portion provided in the fixing unit engages with a positioning member provided in the two-side conveyance unit at the time of closing the two-side conveyance unit, thereby positioning the drive roller and the driven roller.
Incidentally, in the image forming apparatus having the two-side printing mode, when a positional deviation occurs between a reverse roller pair conveying a sheet to the duplex conveyance path in accordance with the opening and closing of the two-side conveyance unit and the conveyance roller pair on the duplex conveyance path, the positional accuracy of an image formed on the rear surface of the sheet is degraded.
In the image forming apparatus disclosed in JP-A-2009-75478, the positioning protruding portion and the positioning member are provided in the vicinity of one conveyance roller pair among a plurality of conveyance roller pairs provided on the duplex conveyance path.
For this reason, a configuration is provided in which the positioning accuracy of one conveyance roller pair and the reverse roller pair becomes satisfactory, but the positioning accuracy of the other conveyance roller pairs on the duplex conveyance path and the reverse roller pair has a problem.
In addition, since a configuration is provided in which the duplex conveyance path is divided by the opening of the two-side conveyance unit, the positioning accuracy of the reverse roller pair and the duplex conveyance path also has a problem, which leads to a concern for the occurrence of a positional deviation of an image formed on the rear surface of a sheet.